The present invention relates to hydraulically-actuated propulsion devices and more particularly to a propulsion apparatus for use with selected tools to permit insertion and positioning of the tools into borehole tubular members, including well casing and tubing, tubular drill string members or pipeline sections in response to fluid pressure acting on the propulsion apparatus.
Wireline logging and well completion tools are inserted into typical vertical or slightly deviated oil and gas boreholes by gravitational action on the end of a cable (the "wireline") spooled from a drum and winch arrangement on the surface. The wireline tool is lowered into the borehole to a desired depth location and then is raised at a preselected rate during logging operations, or raised or lowered to accomplish other operations. However, in highly deviated or horizontal boreholes, the wireline tool and wireline cable will engage the sides of the borehole walls and the friction between the assembly and the borehole walls prevents continued movement into the borehole.
Similarly, pipeline inspection tools in above-ground or buried pipelines must be "pushed" or "pulled" through the pipeline in order to traverse the length to be inspected. In large diameter pipelines, fluid pressure or air pressure actuated "pigs" or locomotives pull the measurement instruments through the pipeline length to be investigated. In many cases, it is often necessary to have access to each end of the pipeline section to be investigated in order to provide cable systems for pulling the tool through the pipeline section. In extremely long pipeline sections, it would be advantageous to be able to propel and position the inspection tools from one accessible end and then recover the tool from the same end.
Another tool positioning problem in downhole tubular members occurs in drilling deviated wellbores ("directional drilling") using drilling fluid driven drilling motors ("mud motors") that turn the rotary drilling bit on the end of the drill string instead of the entire drill string being driven by a rotary turntable located on the drilling rig. The mud motor is driven by drilling fluid transported downhole through the drill string, i.e., tubular members such as drill pipe and drill collars which make up the drill string. A "steering" tool which controls the direction of drilling of the mud motor is positioned just above the mud motor within the drill string and generally must be properly "aligned" with respect to the mud motor. The steering tool is generally positioned downhole using a wireline cable, which is an expensive and time consuming operation. However, when a well deviation exceeds .+-.50.degree., the positioning of the steering tool can no longer be accomplished by gravity powered methods such as using a wireline cable. Further, it has been difficult to properly "align" the steering tool with the mud motor for a known azimuth direction, and ideally, the mud motor is not operational while the steering tool is being properly positioned.
Accordingly, previously in highly deviated and horizontal oil and gas wells (which are increasing in popularity due to many technological and production advantages over vertical boreholes) wireline tools were not usable and the well logging and completion tools had to be "pushed" or "oonveyed" into the deviated or horizontal borehole by means of tubing strings or flexible coiled tubing pushed down into the borehole. Similarly, in pipelines, certain inspection tools that are available by wireline could not be used unless "pushed" or "pulled" into the pipeline using tubing or by cable if both ends of the pipeline were accessible and the length was not too great. Such tubing conveyed systems are much more expensive to operate than a conventional wireline tool, because of the expense of the great lengths of tubing necessary to insert the tool and because of the expense and complexity of the means necessary to drive the tubing string into the deviated or horizontal borehole or pipeline section and to later retrieve the tubing string.
Accordingly, one feature of the present invention is to provide propulsion apparatus that is fluid actuated for conveying and positioning selected conventional tools in tubular members, especially those that are highly deviated or horizontal.
Another feature of the present invention is to provide a propulsion apparatus that, once hydraulically positioned in the tubular member, responds to a selected fluid pressure change for actuating the propulsion apparatus to allow equalization of the hydraulic pressure acting on the propulsion apparatus.
Still another feature of the present invention is to provide a fluid actuated propulsion apparatus embodiment for conveying and positioning a selected tool within a tubular drill string and permitting fluid above the propulsion apparatus to be discharged through a closed end of the tubular drill string.